To date, a number of disease control agents for use with agricultural and horticultural crops have been proposed. For example, Patent document 1 discloses a tetrazolyl oxime derivative represented by formula (1-a) having excellent drug efficacy in useful plants, and suggests using the compound as a plant disease control agent.

In formula (1-a), A represents a halogen atom, alkyl group, alkoxy group, methane sulfonyl group, trifluoromethyl group, aryl group, cyano group or nitro group; n represents an integer of 0 to 5; Y represents an alkyl group; Het represents a substituted pyridyl group or a substituted thiazolyl group.

This tetrazolyl oxime derivative represented by formula (1-a) can be produced by reacting a 1-alkyl-5-benzoyl-1H-tetrazole derivative with a hydroxylamine to obtain a tetrazolyl hydroxyimino derivative represented by formula (V), followed by reacting the obtained tetrazolyl hydroxyimino derivative with a Het-CH2L (provided that L represents a chlorine atom, bromine atom or iodine atom) in the presence of a base (for example, sodium hydride, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, triethylamine, pyridine, N,N-dimethyl aminopyridine or the like).

The 1-alkyl-5-benzoyl-1H-tetrazole derivative represented by formula (IV), which is used as a raw material of this reaction, can be obtained by a method described in Non-patent document 1. Namely, the 1-alkyl-5-benzoyl-1H-tetrazole derivative represented by formula (IV) may be obtained by reacting a tetrazole derivative represented by formula (b-1) with an organic lithium compound to obtain a derivative represented by formula (b-2), and reacting the obtained derivative with an ester compound represented by formula (b-3) to obtain a derivative represented by formula (b-4), followed by causing an acid to act upon the obtained derivative.